CMake, Boost: Removed linking with filesystem, linking with system only with Boost 1.35.0 and above

Filesystem is no longer required, thus removed.
System was introduced with 1.35.0, so the link would file with older versions of Boost.
ViennaCLCommon.cmake: Source-package no longer builds test by default.

The tests require uBLAS to be available, which is not necessary the case on the target machine.
If tests should be build, configure with
 cmake .. -DENABLE_UBLAS=ON -DBUILD_TESTING=ON